Eggshell Myth: good idea or all cracked up?

We’ve heard dozens of home remedies to control slugs, some effective, some that don’t work at all. One remedy we’ve heard many times is to place a band of crushed eggshells around any plants you want to protect. In theory, any slug crossing this barrier will lacerate its soft belly and die the “death of a thousand cuts”. So does this idea really work? Well, crushed eggshells do have sharp edges and slugs do crawl around on their bellies. But we decided the only way to know for sure was to test.

The Procedure

We placed two identical leaves of lettuce in the center of our largest slug holding pen. Next, we surrounded one of those leaves with crushed eggshells and left the other open to any passing slug or snail. Then we set up the time-lapse camera and called it a day. (Slugs and snails do their best work at night – we don’t.)

Our critters are fed a balanced diet every day so we reasoned that if eggshells were really an effective deterrent the slugs would gladly go looking for another meal. Like the all-you-can-eat lettuce bar right next door.

So what happened? The results surprised even us.

Experiment #1

The setup: two lettuce leaves, one surrounded by eggshells. Add slugs.

7:13 pm: Guess who’s coming to dinner

8:01 pm: Three more guests show up – invitations please?

7:09 am – complete destruction

Slugs 1 : Eggshells 0

After just twelve hours the lettuce leaf “protected” by crushed eggshells is completely gone and the unprotected leaf has hardly been touched! What’s going on here?

First, the slugs are actually attracted to the eggshells. Even though these shells had been rinsed off they still had egg residue and bits of membrane on the inside. Apparently this is yummy stuff if you’re a slug.

Next, the slugs clearly don’t care about crawling across the eggshells. They didn’t just nibble around the edges, they lounged across them like the softest feather bed.

Still, we detected a flaw in our first experiment – slugs love those eggy bits! We wondered if eggshells surrounding plants in your garden would be more effective? Maybe rain or irrigation would wash away any egg residue and the slugs would then be turned away. One experiment is rarely enough to draw a scientific conclusion so we decided to try again.

Experiment #2

The setup: two lettuce leaves, one surrounded by eggshells. But this time we aged the eggshells by leaving them out in the rain for two weeks.

9:28 pm: Once again the slugs clearly don’t mind the eggshells.

5:32 am: This time the unprotected leaf gets eaten too.

By the following morning results of our second test are in and both leaves are substantially reduced.

Conclusion: This garden myth isBusted.

Eggshells won’t stop slugs from eating your plants, period. Worse yet, if the shells have any residue left on them they can actually attract slugs! Better to save those eggshells for the compost and trya method that really works.